The Rangers are like a heavyweight in the middle rounds of a grueling title bout, conserving energy, throwing metaphorical punches in short bursts, no longer on their toes, but comfortable in the clinches and on the ropes while dug in for the long haul.

They play in spurts now, these Black-and-Blueshirts, and if anyone suggests — let alone insists — this is not the byproduct of the club having been forced to grind through a pair of seven-game series to open this tournament following an 82-game season in which maximum effort was demanded and expended on essentially every shift, then that person is spinning a tale.

But here’s the crux of the matter: The Rangers are surviving this way, are up 2-1 over the Devils in the Eastern finals after yesterday’s Game 3, 3-0 victory at the Rock playing their way, with so much of it made possible by the Swedish security blanket that covers their net.

Historically great goaltenders affix their signatures not only to games, but to their respective team’s style. Ken Dryden and Martin Brodeur won multiple Stanley Cups making critical saves at critical moments behind staunch defenses that yielded relatively few chances. Mike Richter won a Cup and Grant Fuhr won a handful making huge saves behind teams that pressed the attack but were prone to yield the odd-man rush.

And Henrik Lundqvist, the coolest man in the room unless Brad Richards enters it, and then both can claim that mantle; this royal goaltender is made for this Rangers team that often regards the defensive zone as a comfort zone and can spend shifts at a time back there without coming undone or unglued.

Yesterday provided another example of The King’s value to his tired team, for not only was he unflappable with the puck in his own end for most of the first 30 minutes, Lundqvist’s sprawling glove save on an Ilya Kovalchuk breakaway 45 seconds into the second denied the Devils the emotional lift — not to mention the lead — they so desperately required.

“As a goalie, you don’t get the choice of when you want to be there for your team,” Lundqvist told The Post after recording his second shutout of the series and third of the tournament. “The most important thing for a goalie is to be there when you’re needed by the team, not when it might be easiest for you.

“It’s exciting for me to know that I can come through when the team needs me. That’s what this game is about, being there and competing for your teammates.”

There’s no denying the “compete” plasma that courses through the veins of every Blueblood in the room. There is also no denying the fatigue factor afflicting the Rangers, though no player would ever admit to it and no coach in his right mind would ever offer that up as an explanation or excuse.

It is no coincidence nearly all of the Rangers’ best offensive shifts yesterday came with Chris Kreider on the ice, with the 21-year-old winger getting time on the left with both Richards and Marian Gaborik and Derek Stepan and Ryan Callahan, exchanging places for a number of shifts with Carl Hagelin.

Kreider isn’t merely a freshman in the league; he is fresh, coming off a 44-game season with Boston College, and it shows on almost every turn out there, strong on the puck, able to keep the puck on his stick and as effective below the hash marks yesterday, notably with Richards and Gaborik, as in open ice.

The Rangers regained their game late in the second and throughout the third. Callahan was indefatigable, breaking through for an empty-netter. Richards recorded a signature Big Moment play by cleanly winning a left wing faceoff from Patrik Elias to set up Dan Girardi’s power-play score at 3:19 of the third for the game’s first goal.

But in the end, and at the beginning, there was Lundqvist.

There is always Lundqvist for the Rangers, the goaltender who has affixed his signature to the franchise.